HP Zbook recognises monitor, but does not show video

[DaKo2025]

I use the Sitecom USB-C to DUAL HDMI Adapter + PD in combination with my HP laptop (ZBook with thunderbolt connection) and two Philips 223S monitors.

Suddenly it stopped working. When connected, Windows 11 does connect to the monitors (also confirmed by the display setting screen), but no video is shown on the monitors. Another HP laptop works fine in this combination. And when I connect the philips monitors  the HDMI port on the laptop, it also works fine.

So I suppose the monitors are fine, and the sitecom adapter works fine. Since it uses windows drivers for operation, could that be part of the problem (and solution)?

Recently Windows updated (KB5056579 / KB5062553 / KB5063326). Before it worked fine, after these updates, it stopped.

I  tried to figure out what happened, and how to solve, but seem not to find the cause and proper solution. Suggestions for troubleshooting are welcome

[banhien]

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@DaKo2025 wrote:

So I suppose the monitors are fine, and the sitecom adapter works fine.

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@DaKo2025 

Wrong. What is you sitecom hub (many of them)? It may NOT compatible with your zBook at all. Please note: you can NOT compare cheap USB-C hubs with some HP Thunderbolf docks.

Regards.

Regards. 

[DaKo2025]

As mentioned, it was working fine, untill it suddenly stopped. So compatability should not be an issue. The type of HUB is CN-398

I made some progress. It now sometimes work, sometimes not. It seems that after entering sleep mode, my monitors will not show video. After a few times disconnecting and reconnecting, I have a chance they will work again. Untill the sleep mode kicks in again.

Can it be as simple as a faulty connection? It feels like a firm, tight connecion. Can I test the thunderbolt-port in some way? 

I am very aware the comparison with a HP dock is unfair. That is why I do not compare them. It is just the sudden issues, after working fine for some years. 

[banhien]

@DaKo2025 

If you wish to test the Thunderbolt port(s) you can use HP Thunderbolt docks or at least USB-C G5 dock. I tested my Zbook Firefly G10 with my HP USB-C dock and they work. My plan is to buy an HP Thunderbolt dock but my money a bit short at this time.

Regards.

[DaKo2025]

Thanks for your reply. That is not really a test, it is more a gamble. I have connected my phone to the thunderbolt port, and noticed a very low charging power of 0,7-1,5 watt. Sometimes it increases to 7 watt. So my though is that the power output is sometimes so low, that the sitecom Hub is not able to forward video. I know it is a crappy test with the phone, but it makes me think...   

[banhien]

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@DaKo2025 wrote:

... So my though is that the power output is sometimes so low, that the sitecom Hub is not able to forward video. I know it is a crappy test with the phone, but it makes me think...   

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@DaKo2025 

That why I asked what is your hub

Regards.

[DaKo2025]

Thanks, I mentioned my hub in the earlier post. Any suggestions to determine the cause of this annoying issue?